Test of Hearing And Pure-tone Audiometry

IN THIS PRACTICAL WE WILL DO TUNNING FORK TESTS AUDIOMETRY

Objectives To interpret the audiograms. To perform Rinne and Webber tests and interpret the results. Use the audiometer to plot the frequency intensity recording and construct the audiograms . To interpret the audiograms.

conductive Conductive hearing ability is mediated by the middle ear composed of the incus, malleus, stapes, and eustachian tube.

Sensorineuronal Sensorineural hearing ability is mediated by the inner ear composed of the cochlea with its internal basilar membrane and attached cochlear nerve (cranial nerve VIII).

Air conduction This test assesses sensitivity when the signal is transmitted through the outer, middle, and inner ear and then through the brain to the cortex.

Bone conduction This technique assesses sensitivity when the signal is transmitted through the bones of the skull to the cochlea and then through the auditory pathways of the brain. This type of testing bypasses the outer and middle ear.

TUNING FORK TESTS

Rinne Test Technique First: Bone Conduction Vibrating Tuning Fork held on Mastoid Patient covers opposite ear with hand Patient signals when sound ceases Move the vibrating tuning fork over the ear canal Next: Air Conduction Near, but not touching the ear Patient indicates when the sound ceases

Rinne Test Normal: Air Conduction is better than Bone Conduction Air conduction usually persists twice as long as bone Referred to as "positive test" Abnormal: Bone conduction better than air conduction Suggests Conductive Hearing Loss. Referred to as "negative test"

Weber Test Technique: Tuning Fork placed at vertex of the skull Normal: Sound radiates to both ears equally Abnormal: Sound lateralizes to one ear Ipsilateral Conductive Hearing Loss OR Contralateral Sensorineural Hearing Loss.

Pure-Tone Audiometry

Pure tone A pure tone is a single frequency tone with no harmonic content (no overtones). This corresponds to a sine wave.

Pure tone Pure tone

Audiometry Is the procedure by which the nature of hearing disabilities e.g. conductive or sensory neural deafness are determined.

Audiogram It is a graph that shows the audible threshold for standardized frequencies as measured by audiometer.

Audiogram The audiogram reflects hearing sensitivity with frequency charted on the X- axis (Hz) and intensity on the Y-axis (dB).

Audiometer Is an electronic oscillator capable of emitting pure tones of various frequencies through ear phones to the subject.

Masking Masking presents a constant noise to the non-test ear to prevent crossover from the test ear. The purpose of masking is to prevent the non-test ear from detecting the signal (line busy), so only the test ear can respond.

Audiogram

Pure tone Audiometry In a sound proof room person is seated comfortably. Ear phones are applied which are color coded. (Red for right ear, Blue for left ear). Masking sound is delivered to the non-test ear. Start with a frequency of 125Hz. & 0 dB. Gradually increase the dB. till person hears the sound & respond. Mark the threshold intensity on the audiogram paper.

Contd… Find the threshold of hearing from 125 Hz. to 8000Hz. & mark on the audiogram paper. Join the points to make air conduction audiogram. Place the bone vibrator over the mastoid process. Deliver the sound through the vibrator & find out the threshold of hearing for different frequencies of sound.

Contd… Use different sign to mark the bone conduction audiogram. Select the other ear and repeat the whole procedure.

Entomed Audiometers SA203

Pilot hearing test audiometer

TYPES OF HEARING LOSS Conductive hearing loss Sensorineural hearing loss Mixed hearing loss

Conductive Hearing loss (deafness) The abnormality reduces the effective intensity of the air-conducted signal reaching the cochlea, but it does not affect the bone-conducted signal that does not pass through the outer or middle ear. Examples : perforated tympanic membranes, fluid in the middle ear system, or scarring of the tympanic membrane. Pure-tone air-conduction thresholds are poorer than bone-conduction thresholds by more than 10 dB.

Conductive deafness

Sensorineural Hearing loss (deafness) This type of hearing loss is secondary to cochlear abnormality and/or abnormality of the auditory nerve or central auditory pathways. Because the outer ear and middle ear do not reduce the signal intensity of the air-conducted signal, both air- and bone-conducted signals are effective in stimulating the cochlea. Pure-tone air-conduction and bone-conduction thresholds are within 10 dB.

Sensorineural

Mixed Hearing loss This type of hearing loss has sensorineural and conductive components. Pure-tone air-conduction thresholds are poorer than bone-conduction thresholds by more than 10 dB, and bone-conduction thresholds are less than 25 dB.

Mixed Hearing Loss

DEGREES OF HEARING LOSS Normal hearing (0-25 dB) Mild hearing loss (26-40 dB) Moderate hearing loss (41-55 dB) Moderate-severe hearing loss (56-70 dB) Severe hearing loss (71-90 dB) Profound hearing loss (>90 dB)

COMMON AUDITORY DISORDERS Presbycusis (age related hearing loss) Otitis media: This condition is marked by fluid in the middle ear space. Noise-induced hearing loss. Otosclerosis: The condition is caused by stapedial fixation in the oval window, stiffening the middle ear system. Ménière disease.

Presbycusis

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